Method of making electrical coils



April 25, 1950 P. A. D'ORIO 2,505,104

METHOD OF MAKING ELECTRICAL COILS Filed June 13, 1946 Timing L SO 52 Mechanism INVENITOR. Put A. DOrio BYW@M A T'I'ORA'EYS Patented Apr. 25, 1950 METHOD OF MAKING ELECTRICAL COILS Pat A. DOrio, Oak Park, 111., assignor to Belmont Radio Corporation, Chicago, 111., a corporation of Illinois Application June 13, 1946, Serial No. 876,552

2 Claims. 1

The present invention relates to a method of making electrical coils and more particularly to a process of manufacturing built-in type loop antennas.

Loop antennas of the built-in type have been extensively employed in recent years in the radio industry. Such antennas or coils are adapted for assembly as an integral part of a radio receiving set and since they are usually placed within the radio cabinet, the size or bulk of the coil directly affects the size of the cabinet and hence, the over-all cost of the set. An electrical coil or windin which is suitable for use as a built-in type of radio antenna usually comprises a flat, either elliptical, circular or rectangular, winding which is often referred to as a pancake winding in which a suitable electrical conductor is spirally wound one turn on the outside of the next turn with the adjacent turns of the conductor insulated from one another either by air or a suitable insulating material.

In a prior copending application, Serial No. 650,063, filed February 25, 1946, now abandoned, and assigned to the same assignee as the present application there is disclosed and claimed a method of manufacturing a coil in which an insulated conductor or an uninsulated conductor with intervening layers of insulation is arranged in the form of a coil so that the insulating material which is preferably a thermoplastic or a thermosetting material is in engagement between adjacent turns. A self-supporting coil is made in accordance with my prior invention by heating the insulation by passing current through the winding whereby the insulation of adjacent turns is caused to fuse to ether and cohere. The method of my above-mentioned prior patent has been used commercially and many coils have been manufactured by that method. It has been found that due to the fact that the conductor which is usually formed of copper cools off more slowly than the surrounding insulation which fuses, there is a subsequent contraction of the copper conductor as it cools with the result that shearing stresses are set up in the insulationwhich has set causing occasional separation of adjacent windings. Although the number of rejects by the prior method is relatively small, it would be desirable to provide a method of manu-' facturing a coil in which the above-mentioned difllculty is completely eliminated.

. Accordingly, it is an object of the present invention to provide a new and improved method for manufacturing electrical coils or windings.

It is another object of the present invention to provide a method of making coils of the abovementioned type in which the number of rejects is reduced substantially to zero.

Still another object of the present invention is to provide a new and improved method for manufacturing electrical coils or windings of the self-supporting type wherein heating causes the fusing together of the adjacent layers of insulation surrounding the conductor forming the winding and wherein the conductor is substantially not heated during the fusing operation.

Further objects and advantages of the present invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention, reference may be had to the accompanying drawing in which:

Fig. 1 is a top plan view of a pancake electrical winding made in accordance with the present invention;

Fig. 2 is a somewhat schematic view of apparatus employed in carrying out one step of the process of the present invention;

Fig. 3 is an enlarged perspective exploded view of a portion of the a paratus of the present invention as employed in-Fig. 2; and

Fig. 4 is a partially schematic view illustrating one embodiment of the heating step of the present invention.

The process for making an electrical coil in accordance with the present invention is illustrated specifically in connection with the manufacture of a pancake type coil wherein a conductor insulated with a thermosetting or thermoplastic insulating material is spirally wound on an insulating supporting member positioned between two plates which may either be constructed of conducting material or if constructed of insulating material are provided with metallic liners as will become apparent from the following description. The winding is made self-supporting by causing the insulation thereof to act as the dielectric of a capacitor supplied'with a high frequency alternating current so that the fusingheat for the thermosetting or thermoplastic insulating material comes from the dielectric heat loss in the insulation.

Referring now to Fig. 1 of the drawing, there is illustrated an electrical winding l0 manufactured in accordance with the present invention. This winding comprises a length of electrical conductor ll, spirally wound in elliptical form and having a thickness in a direction normal to the drawing of Fig. 1 of one turn. The electrical conductor II in the coil I is illustrated as having a coating of insulating material l2 thereon. It should be understood that although the invention is specifically disclosed in connection with manufacturing an antenna winding of elliptical shape it could equally well be used to produce a winding of circular or some other shape. It should also be understood that this invention could be applied to the manufacture of any coil in which the adjacent turns are so arranged as to have their insulated surfaces in physical engagement.

Preferably the winding i0 is formed from insulated wire II which is built up or wound between a pair of plates l3 and I4 forming the mandrel of a winding machine l5 schematically indicated in Fig. 2 of the drawing. These plates I 3 and I4 are shown in greater detail in Fig. 3 of the drawing and preferably comprise a pair of smooth finished flat members formed of conducting material. The plate l3 is provided on one side with a stub shaft I6 which may be inserted into the hollow end of the rotary shaft H of the winding machine I! driven by a suitable winding motor l8 through suitable pulleys l9 and and a belt 2|. The shaft I! is illustrated as being rotatably mounted in one or more bearin s such as indicated at 22. In order that the stub shaft 16 on plate l3 may be removably connected with the winding machine shaft i! a suitable set screw 23 may be employed in shaft l? at its hollow end whereby rotation of the shaft I 1 causes rotation of the shaft l6 and consequently also rotation of the mandrel comprising the plates l3 and I4.

As is best shown in Fig. 3 plate I 8 is provided with a raised portion 24 on the side adjacent plate 2 4 which serves as the core or spool upon which the wire II is wound to form electrical coil Ill. Although the portion 24 is referred to as a raised portion integral with the plate i3, it may also comprise a separate removable member if desired. It will furthermore be understoodthat the portion or core 24 may have any desired shape depending upon the form of the coil 50. However, since an elliptical coil is illustrated in Fig. 1 of the drawing, the port on or core 24 is illustrated as of elliptical shape to conform with the central opening in the winding it of Fig. 1. The plate I3 is also provided with a pair of aligning pins 25 extending from the raised portion 24 in a direction parallel with the axis of the stub shaft [6. The aligningpins 25 are adapted to be inserted in suitable openings 25 in cooperating plate M which latter plate is also provided with suitable fastening means indicated at 2?, having a threaded end 27d adapted to threadedly engage with the end lBa of the stub shaft 56 which preferably extends almost through the plate l3 as is clearly indicated in Fig. 3 of the drawing. Fastening means 21 is also provided at its other end with a manipulating means such as a knurled knob 21?) so that the two plates 53 and i4 can readily be fastened together in the manner indicated in Fig. 2 of the drawing or taken apart as shown in Fig. 3. The width of the winding space defined between plates i3 and i4 is controlled by the raised portion or core 24 of plate l3. This space is adjusted so as to be just large enough to accommodate a single width of the insulated wire ii in the event that an insulated wire is employed. with this arrangement it is clear that the wire will be held "in place since the space between plates II and I4 insures proper positioning thereof. It should be understood that if the diameter of the wire to be employed in constructing the electrical winding l 0 is to be greater than the amount core 24 is raised from the surface of plate It, a suitable shim not shown of the same configuration as raised portion 24 may be inserted between the plates, the shim being provided with suitable openings cooperating with the aligning pins 2! to support the same on the plate It. By employing an assortment of shims of various sizes electrical windings employing any size wire may be constructed with the same winding apparatus.

As illustrated in Fig. 2 of the drawing, the wire i2 is spirally wound on the core or raised portion 24 between plates l3 and I4 from a-suitable supply reel 28 rotatably mounted in any suitable manner as is schematically indicated.

In order to anchor the ends of the winding l0 and so that they may be available to carry out a subsequent step in the process of manufacture to be described hereinafter, plate i4 is provided around the outer edge thereof with a series of notches 29 best shown in Figs. 3 and 4 of the drawing, and a pair of split pegs 30 which extend from the side of plate l4 opposite the side thereof adjacent plate l3. When it is desired to start a new coil ID the end Ila of the wire II from the reel 28 is placed between plates l3 and i4 and allowed to extend out of one of the notches 29 as is shown in Fig. 4 of the drawings. This end Ha of wire II is anchored to the one of the split pegs 30 most closely adjacent to the particular notch 29 through which the wire ll extends. It will be obvious that the depth of the notches 29 should be such as to extend to the outer periphery of the raised portion 24 whereby the end of the inside turn of the coil. l0 may be brought out at the bottom of a particular one of these notches 29. The reason why a plurality of notches such as 29 are provided is to permit one to manufacture coils having different predetermined values of inductance with the same apparatus. To accomplish this the winding may require a fractional turn and accordingly for coils having different inductances it is desirable to have a series of notches 29 judiciously spaced around the periphery of plate l4. In production. it has been found that the coils made by this process have uniform inductance thus requiring a minimum adjustment when placed in the radio sets for which they were designed. Also, it is sometimes desirable to provide a winding having more than two terminals as, for example, a transformer. This is another reason why it is desirable to provide a plurality of notches 29 through which the ends of the wires leading to the plurality of terminals may be brought out.

Upon winding the desired number of turns between plates !3 and i4 the insulated conductor ii is cut off and the other end Hb brought out through another one of the notches 29 and fastened to the other split peg 30 as is shown in Fig. 4. In order to simplify the disclosure the invention is illustrated in connection with manufacturing an electrical winding I0 having but two terminals although it is obvious that additional terminals might be brought out through the notches 29 provided for this purpose.

It should be understood that the winding apparatus described thus far and the particular 7 construction of the mandrel comprising the i drawing.

plates l3 and I4 formsno part of the present invention and any suitable apparatus for wind- I ing the conductor H to produce a spirally wound pancake winding ll .of any configuration may be employed m well as apparatus for winding. a helix,

so long as'the adjacent turns have their insulation in physical engagement.

If it were desired to remove the completed winding from between plates l3 and i4 immediately following the winding operation it is obvious that the coil. would not retain its desired shape and the adjacent turns would separate from one another. In prior art arrangements various rather complicated processes were employed for causing the insulation of the adjacent turns to cohere to each other whereby acoil which is completely self-supporting without any additional supporting structure is obtained. In accordance with the present invention, this is accomplished in a simple and inexpensive manner by employ ing an insulated wire ll, the insulation I! of which preferably comprises a thermoplastic insulating material but might conceivably also comprise a thermosetting insulating material. A

' very suitable thermoplastic insulating material for this purpose is P lyethylene which is extensively used for insulating electrical conductors. 4

In accordance with the present invention, the

- insulation l2 on the winding I is heated without substantially heating the electrical conductor ii by causing the insulation l-Z to become the dielectric of a capacitor connected to a source of high frequency alternating current. Any suitable source of high frequency alternating current may be employed and as illustrated in Fig. 4 of the drawing. there is provided an oscillation generator generally indicated at 38. Oscillation generator 36 may comprise anystandard form of generator for producing high frequency oscillations. In Fig. 4 this generator has been illustrated. as comprising the-well known Colpltts In order to perform certain control functions such as energizingthe oscillation generator 38 for a predetermined time, there is provided an electric switch or circuit breaker It in the input circuit of the oscillation generator 38. When this switch ill is closed it is adapted to bridge contacts 5| .so that high frequency oscillations may be obtained at the output circuit of the oscillation generator .38 to be described hereinafter. Electric switch or circuit-breaker 50 is adapted 'to be controlled by a timing mechanism generally indicated at a: which upon closing of switch or circuit breaker 50 will cause reopening thereof after a predetermined time which time is ad- Justable at the will of the operator.

' In the event that the source of direct current fed to the input circuit of the oscillation'generator 36 is obtained by rectifying an alternating current, it may be desirable to provide a filter comprising a choke coil 53 and a by-pass condenser 54 as is indicated in Fig. 4 of the drawing.

Such a filter will impede the passage of high frequency power into the rectifier supplying the direct current energy to the input of the oscillation generator 36, v

The high frequency output of the oscillation generator 38 is obtained by inductively coupling oscillator including an electric discharge valve 31 having an anode 33, a cathode 39 and a control electrode or grid 40. The oscillating action of the electric discharge valve 31 is controlled by a tuned or resonant circuit generally referred to as atank circuit comprising the serially arranged inductance 4| connected in parallel with serially arranged capacitors 42 and 43. The cathode 39 of the electric discharge valve 31 is connected to a point on the tank circuit between capacitors 42 and 43 which act as avoltage divider. The

lower terminal of the tank circuit is connected.

to control electrode or grid 40 through a grid blocking capacitor-44. A grid leak circuit is provided between control electrode 40 and cathode 39 which comprises a resistor 45 and an inductance 46. Preferably cathode 39 is grounded as is indicated at 41. The upper terminal of the tank circuit is connected to anode 38 through a winding 56 to the inductance 4! whereby high frequency oscillations appear across the terminals 51 and 58 of winding 56 when these terminals are connected to a suitable load. As indicated in Fig. '4, the terminal 51 is connected to one of the plates such as l3 or l4 forming the mandrel of the winding machine while the other terminal 58 is connected to one end of the conductor Ii. If the plates l3 and 14 are formed of conducting materiaLthey are electrically interconnected by virtue of the member 21, the mem-' hers I! and portion 24 if the raised portion 24' is also formed of conducting material." In such a case both plates i3 and I4 of .the mandrel are electrically connected to the terminal 51, this arrangement, it will be obvious that two parallel condensers are formed with the conductor ll forming a common plate for the two condensers while the conducting plate i4 and the conducting plate I3 each form a plate of a. different one of the condensers. The high frequency current which is preferably of theorder of one megacycle or morecauses'heating of the dielectric comprising the insulation I2 with the result that the adjacentengaging layers of thermosetting or thermoplastic insulating material are caused to fuse and cohere without appreciably heating the conductor I I. The length of time that the high-frequency current is supplied for the dielectric heating process is controlled by circuit breaker Ill; Since there is substantially no heating of the conductor, 1 I, there is no possibility of shearing stresses being developed in the insulating material upon cooling of the conductor after a plate blocking condenser 48 in order to inulate the anode 3! from control electrode 43, as far as the direct current potential applied to the anode-cathode circuit of electric discharge valve 31 to be described hereinafter is concerned, while still maintaining anode 3t and the upper terminal of the tank circuit'at the same high frequency potential. A source of direct current'potential is applied across the anode-cathode circuit of the electric discharge ;valve 31 which will be referred to as the input circuit of the oscillation generator 36. This source of direct current is indicated by a battery 49 shown in Fig, 4 of the the insulating material has set;

If. it is desired to employ a mandrel in which terminal I! while the other plate would be With connected to terminal 58. In this case, the dielectric between plates l3 and H would consist of both the conductor Ii and the insulation [2. The dielectric heating of this composite dielectric would cause much greater heating of the insulation I! by. virtue of the fact that it is a high loss insulation as contrasted with the low loss conductor I I. In any event, either method would obviate the thermal lag resulting when the conductor is heated to a high temperature and cools subsequently to the fusing or setting of the insulation.

The antenna l constructed by the method of the present invention is well adapted to be mounted on the back of the radio cabinet in any suitable manner. The completed winding i0, when properly manufactured in accordance with the present invention, almost looks like a spirally wound electrical conductor embedded in a flat unitary. insulating member due to the thermoplastic welds between adjacent turns of the insulated winding.

It should be understood that the same results i can be obtained by using an uninsulated wire and interwinding it with a thermoplastic tape or strip fed from a separate reel or spool. In view of the detailed description included above it is believed that the process of the present invention will be obvious to those skilled in the art.

It should be understood that the present invention is not limited to the particular process disclosed and described in detail above and that changes and modifications may occur to those skilled in the art without departing from the spirit and scope of the present invention. It is, therefore, aimed in the appended claims to cover all such changes and modifications.

What I-claim as new and desire to secure by Letters Patent of the United States is:

l. The process of making a self-supporting coil from a conductor having insulation thereon made of thermoplastic or thermosetting material which comprises, arranging the conductor in the form of a flat spiral winding with the insulation of each turn of the winding in physical engagement with the insulation of at least one adjacent turn, placing a conducting plate against lation and being heated to a lesser extent than said insulation.

2. The method of constructing a self-supporting coil from wire having insulation thereon made of thermoplastic or thermosetting material which comprises arranging a length of the wire between a pair of conducting plates in the form of a spirally wound coil with the insulation of adjacent turns in mutual engagement, whereby condenser means is formed with the wire serving as one electrode, the conducting plates serving as the other electrode and the insulation serving as the dielectric, and applying .a high frequency alternating current between the plates and the wire so that the insulation is heated and is thereby softened and adjacent turns of the coil cohere, with the wire being thereby heated to a lesser extent than the insulation.

PAT A. DORIO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,874,723 Dawson Aug. 30, 1932 2,177,260 Laube Oct. 24, 1939 2,282,759 Gavitt May 12, 1942 2,422,525 Brown June 17, 1947 FOREIGN PATENTS Number Country Date 555,054 Great Britain Aug. 3, 1943 OTHER REFERENCES Hoyler, An electronic sewing machine," reprint from 1943 issue of Electronics (7 pages). 

